The present invention relates to a small-sized automatic nailing machine used for manufacturing packing wooden flasks and the like. The automatic nailing machine is constructed so that it supplies nails in the magazine communicated with a guide hole one by one into the guide hole nose located at the tip thereof. The head of each nail in the guide hole is struck by the tip of a piston rod movable in the guide hole toward the opening at the bottom thereof. The piston rod is driven by compressed air when a trigger on the apparatus is pulled. To make it possible to supply the nails charged in the magazine one by one into the guide hole as described above, heretofore various means have been proposed and put in practice, but there were defects; the automatic nailing machines were complicated in construction and poor in durability, or the nails to be driven were applied with special measures (like sticking a plurality of nails at suitably spaced intervals on adhesive tape or the like), thereby increasing costs as well as the consumption of nails.